That is becaues tpPLC does not actually rename the devices - it just tries to remember which is which. Other PLC utilities actually program the names into the devices, and this is persistent. The way TP-Link devices use the vendor/model/name fields is all wrong though: The entire device identification is in the "name" field, so if you rename the device, the tpPLC utlitiy will not be able to identify the model anymore.